Zigbee2mqtt: [Feature] Add last_changed attribute to all sensors

[CodeFinder2]

Not a bug, just a feature request (or an info if it's already available but was not able to find something like this in the docs).

I was searching for a way to get the time when a sensor has changed lastly (in HA). Many forum posts suggest to use the last_changed attribute of an entity but, unfortunately, all my Z2M created devices /entities do not have that. (If this is possible with HA ingredients only, I am totally fine with that and would be grateful to get to know, how.)

So I would suggest to add such an attribute that reports the time when a sensor has actually changed. Please let me know what do you think about this! :-)
I would say to just reflect state changes, not changes of an attribute. In my setup,
I would like to get the time my front door was left open (= close => open transition) so last_changed should not change when the battery level of that sensor drops, for example.
(I know there is already last_seen but that's obviously something different.) And since there should be a dedicated 'battery entity' for that sensor anyway, last_changedof that entity can report the time of the last battery drop if someone needs it. (Hopefully, I am not mixing terms here.)

Thanks for considering this!

Debug Info

Zigbee2mqtt version: 1.14.0 (latest)
Adapter hardware: CC1352P-2
Adapter firmware version: 2020-04-20 (latest)

[Koenkk]

@emontnemery is the last_changed (or last_updated?) property supported for MQTT sensors?

[emontnemery]

last_changed is built into the Home Assistant states, it's not something that needs to be explicitly supported.
There's an explanation here: https://community.home-assistant.io/t/last-updated-state-and-last-changed-in-lovelave/101701/2

Note that last_changed is not part of the attributes dict.

[CodeFinder2]

Great, thank you! Exactly what I was looking for! For posterity, that's what I ended up using to print the time when my front door's state changed (Z2M v1.14.0, HA v0.111.1):

{{ as_timestamp(states.binary_sensor['0x00158d0002exxxxx_contact'].last_changed) | timestamp_custom('%X', True) }}

Will print something like (in my local time format): "16:00:51". Note that if a sensor starts with a digit (0 here which basically applies to all Z2M created sensors, AFAIK), you cannot use the form:

{{ states.domain.entity_id.last_changed }}

because this causes a syntax error. (domain is, e,.g., binary_sensor or light.)

Error rendering template: TemplateSyntaxError: expected token ',', got 'x00158d0002exxxxx_contact'

[davekr8]

last_changed is built into the Home Assistant states

Is the usage of HomeAssistant a kind of "default use-case"?

I think a "aquisition time" (the timestamp, when the zigbee message is received, before any time consuming processing is done) is a (the only) relevant info. I don't want the second or third service in chain to handle time-stamps, this will add delay and jitter as well.

So a +1 from me for the "last changed" field. I further would propose the wording "aquisition time" and refer those time-stamps as basis for all derived time-stamps, as "last_seen" etc. pp.

What do you guys think ?